Hi there I have a customer that has acquired a 3ph Icecream Batch freezer - Carpigiani LB502
So far they have installed a 10hp Rotary Phase converter to generate 3ph from the 1ph service.
The customer wants to make sure the batch freezer is getting the right quality of hydro to make sure it works consistently. I have done a few tests and am looking for a bit of input regarding voltages. And I have included the numbers off the rating plate on the back of the machine.
The machine has 3 main components: 1. the controls (must not be connected to the generated leg) 2. 3 hp beater motor 8.4FLA 3. 3 hp compressor with water cooling 9.8FLA 78LRA
The phase converter is a Phase-a-matic PAM-1200HD with 10hp idler motor, with a disconnect switch of the generated leg back to the phase converter once the system is running (to prevent startup sequence to kick in).
The utility input is 250v split phase (125v + 125v). The batch freezer is rated at 25a 3ph 208/230v 60hz 3 wire - max fuse size 30a. Manufacturer suggests voltage between 215 and 218 as the best operating range.
Currently here are the voltages (line 3 is the generated leg):
No load line 1-2: 250v line 1-3: 237v line 2-3: 238v
Beater motor load only: line 1-2: 248v line 1-3: 231v line 2-3: 223v
Beater motor and compressor: line 1-2: 246v line 1-3: 225v line 2-3: 221v
When the batch freezer is started up and running to produce ice cream the beater motor turns on first then 3 seconds later the compressor kicks in. The whole process takes about 8 minutes. After that the compressor turns off (and could/should kick back in to keep the temperature steady) with the beater still turning to dispense the icecream.
The batch freezer makes icecream just fine except that the controls that automatically sense and control the consistency of the icecream do not work as intended. If left unattended the machine will continue to freeze the icecream until the beater freezes stuck instead of cycling the compressor at a preset consistency of icecream. Therefore the operator must manually keep an eye on the progress.
I am thinking the high input voltage and difference of voltages between lines have something to do with the controls not working as intended. The machine worked perfectly in a utility 3ph environment prior to moving it to this location.
Not having too much experience with RPC as such - how do I reduce and balance the voltages over all.
1. Possibly I could reduce the 1ph input using 1 buck transformer to reduce to 215-220v BEFORE the phase converter. This would reduce the voltage of the generated leg as well!? as low as 200v under load possibly???
2. Is there a way to reduce the voltages (bucking) of the 2 utility lines only, AFTER the phase converter, leaving the generated leg as is so that the voltages are all closer to the 220-230v range? Would this make the phases or anything go out of sync?
3. If a buck transformer were to be helpful does a 12kVA unit suffice?
4. A 3 phase buck transformer setup of all 3 lines AFTER the phase converter would reduce the voltages of each line from what I understand... defeating goal to balance voltages?
Let me know what any of you think and what my best coarse of action could be (or if I have left out any info that you might need let me know)
The controls are off of 1 and 2. They are not supposed to be off the artificial leg. These machines are run off of phase converters quite often according to the manufacturer help line.
Looking at the wiring diagram the line to the beater motor that is monitored for the ice cream consistency (load of the motor) is the artificial leg... that might be the reason it doesnt reliably read the icecream consistancy. The voltage drops when the compressor kicks in changing the load I guess.
Here is a link to the wiring diagram that I took a pic of
click on the pic and then to the right click on full details.
I was thinking of getting a VFD just for the beater. Though I dont have much experience with them. Can they be set up to have a steady 60hz 220v from my input voltage? --NOT variable as the usual use for them?
I would just try moving the CT to a non-generated leg.
A VFD might be more trouble than it's worth. You would have to find a place to mount it, re-route the power conductors, connect the controls and program the vfd. Then, it's bad to quickly switch the power off and on to a vfd so it adds another complexity to turning off the machine and turning it back on.
You would have to warranty the vfd for a period of time and, if it failed, provide a replacement while the manufacturer decided whether they would pay for the new one - which they probably wouldn't. I love the way vfds handle a motor but I hate dealing with a vfd failure.
Personally, Fredweet, I'd not go with a VSD on any sort of an agitator/beater drive motor and especially with something that has the viscosity of ice-cream. Reason I say that, is because you need to be able to get this product moving for a start, this is where you need the initial "oomph" from a DOL starter, to get the drive unit turning in the first place.
This is only my thoughts on this, I could be way wrong too, I've worked with milk vat agitators in 22,000L refrigerated vats before and getting the blades of the agitator to turn first off with a VSD on it, was just about impossible. What you need to think about is the amount of force required to get that beater turning.
I tried rolling the phases around with no luck yet. However the 24v transformer running off of 1 line of 120v has helped. Though the controls are not reading the ice cream consistency very well yet. So I am going to suggest to the customer to invest in a VFD to get a more balanced 3phase for the beater motor alone.
The icecream mixture at the start is very fluid and it is only up to 14 liters of mixture. Near the end it gets a bit more firm but not more firm than soft serve icecream. So I don't see the motor needing to have too much more oomph to get going.
any input would be great as I don't have too much experience with VFD sizing.
The beater motor is a leeson 3phase 3hp motor with the following details
86.5 NEMA nom Eff
What would be the minimum VFD that would be sufficient.
The single phase current is 1.7 times the three phase current, so the vfd should be either rated for single phase to three phase conversion or double the H.P. rating. (Make sure the vfd will run on single phase)
I like the Leeson VFD and they are the cheapest. However, I had warranty issues with Leeson. Put enough profit in so you can cover a new vfd if there is a problem.
Ok thanks for that info. Would a 3hp 2.2kW VFD run a 3hp motor? If the output of a VFD is 11A @ 220v the output is 2420W (Or rounded to 2.2kW) A leeson model is available to convert from 1ph to 3ph with an output of 2.2kW.